docs: def bulk_lookup(self, api_name, keys):
          """Perform lookup on an enumerable of keys.
  
          Args:
              api_name: a string name of the API. Keys and values are segmented by api_name.
              keys: an enumerable of string keys.
          """
          cached_data = {}
  
          for key in keys:
              value = self.lookup_value(api_name, key)
              if value is not None:
                  cached_data[key] = value
          return cached_data